A class of primary electrochemical power cells which incorporates lithium as the anode material and solid or liquid oxidizers as cathode materials is a commercially available source of power in a small, portable package. These lithium cells have theoretical output voltages in the range of 3 to 3.9 volts and theoretical specific energies in the range of 1000 to 2000 Wh/kg. These cells require nonaqueous electrolytes because of the reactivity of lithium in aqueous solutions. Examples of practical lithium cells are lithium carbon monofluoride (3.1 V), lithium sulfur dioxide (3.1 V), lithium manganese dioxide (3.5 V), lithium thionyl chloride (3.6 V) and lithium sulfuryl chloride (3.9 V). See U.S. Pat. Nos. 3,536,532, 3,567,515, and 4,400,453 The output voltage of 3.9 V for the lithium sulfuryl chloride cell is believed to be the highest output voltage achievable in small, portable commercially available electrochemical power cells.
The lithium anode is stable in these cells because a protective film forms on the lithium surface either by direct reaction with the electrolyte or with an additive in the electrolyte. See U.S. Pat. Nos. 3,567,515 and 4,400,453. In commercially available lithium/thionyl chloride and lithium/sulfural chloride electrochemical power cells, for example, the protective film produced by the reaction between the lithium and an oxyhalide electrolyte is lithium chloride. These films are typically good ionic conductors for lithium ions, but do not transport species present in the electrochemical power cell that could damage the lithium anode.
These lithium electrochemical power cells are commercially viable only because a mechanically stable electrode of blended carbon black and Teflon.RTM. was developed on which solid, liquid or soluble cathode materials could be efficiently reduced. A "solid" cathode material is incorporated into the blend of carbon black and Teflon.RTM.. A "liquid" cathode material may be the solvent component of the electrolyte. A "soluble" cathode material is dissolved in the electrolyte. The process of fabricating carbon black-Teflon.RTM. electrodes for commercial lithium cells is well established and is described, for example, in Turk, C., Modern Battery Technology, p. 291 (1991).
For a number of uses, it is desirable to develop electrochemical power cells with output voltages and specific energies greater than possible with currently available electrochemical power cells.